Traditional incandescent light bulbs are currently being replaced by other light sources having higher energy efficiency and less environmental impact. Alternative light sources include light emitting diode (LED) devices and fluorescent light sources. However, LED devices are expensive and complicated to fabricate and fluorescent light sources are known to contain small amounts of mercury, thereby posing potential health problems due to the health risks involved in mercury exposure. Furthermore, as a result of the mercury content, recycling of fluorescent light sources is both complicated and costly.
An attractive alternative light source has emerged in the form of field emission light sources. A field emission light source includes an anode and a cathode, the anode consists of a transparent electrically conductive layer and a layer of phosphor coated on the inner surface of e.g. a transparent glass tube. The phosphor layer emits is made luminescent when excited by electrons. The electron emission is caused by a voltage between the anode and the cathode. For achieving high emission of light it is desirable to apply the voltage in a range of 2-12 kV.
A suggested power supply provided in conjunction with such a field emission light source is disclosed in US2008185953. In US2008185953, the power supply comprises a bridge rectifier and filtering components, to prevent undesirable emissions, and a voltage-multiplying rectifier for providing high voltage suitable for anode to cathode power of the field emission light source.
However, the implementation of US2008185953 provides undesirable disadvantages in relation to size of the power supply as well as in relation to the efficiency of the power supply. The disadvantages generally derive from the introduction of a large plurality of steps within the voltage multiplier.
Accordingly there is a need for an improved high voltage power supply for a field emission light source, specifically taking into account size of the power supply for allowing integration of the power supply together with the field emission light source.